1. Field of the Invention
The present invention relates to an intake sound adjusting device particularly provided with a mechanism capable of generating an intake sound having a specific frequency band.
2. Description of Related Art
In an internal combustion engine, pulsating (pulsation) sound or noise of intake air introduced into an internal combustion engine due to reciprocating motion of a piston or an intake valve disposed within the internal combustion engine. Since this intake pulsating sound has a wide band range, this is generally considered as “noise”. In order to reduce such intake pulsating sound as noise, a resonator or like is generally disposed in an intake passage to thereby reduce noise of the specific frequency range calculated on the basis of the Helmholtz's Resonance Theory.
However, for some cars such as called “sporty cars”, it is required to generate a vigorous powerful intake sound in a vehicle interior in order to produce an acceleration feel, and in order to satisfy such requirement, in the known art, there is provided a sound quality controlling device capable of producing a powerful intake sound in the vehicle interior only by amplifying a desired frequency band region or area of the intake sound of the wide band range or area.
For the sound quality controlling device mentioned above, prior art provides some sound quality controlling devices in which various attempts have been made for the purpose of tuning a sound pressure characteristic of a desired frequency band.
For example, Japanese Patent Laid-open Publication No. 2005-139982 (Patent Document 1) discloses a sound quality controlling device equipped with a resonator, which is provided with a resonator body (resonating member) oscillating in response to intake air pulsation in a intake unit, a volume chamber connected to the intake unit through the resonating body, and a volume chamber opening section communicating the interior space of the volume chamber with an external side. The interior space of the volume chamber and the interior of the intake unit is sectioned by the resonator body, and by the oscillation of the resonator body, the sound pressure of the specific frequency band area is released externally from the volume chamber opening section.
Furthermore, an intake device disclosed in Japanese Patent Laid-open Publication No. 2006-83787 (Patent Document 2) is provided with an intake passage for introducing sucked air into the internal combustion engine and a resonator passage branched from the intake passage, in which the resonator passage has one end opened to atmosphere and the other end connected to the intake passage. The resonator passage has a length set to be suitable for applying sound pressure of the specific frequency band area to the intake (sucked) air.
However, according to the structures or constructions of the sound quality controlling device disclosed in the Patent Document 1 and the intake device disclosed in the Patent Document 2, there may cause a case where a sound in an area other than the specific frequency band area, which constitute cause or factor of an offensive loud noise or a vehicle exterior noise. Moreover, in a case of changing the specific frequency band in the sound quality tuning operation, it is obliged to re-design volume or size of the volume chamber and the resonator, which makes it difficult to easily perform the sound quality tuning.